In recent years, solid-state imaging devices (image sensors) that photograph subject images are widely used in cameras, cellular phones, and the like. Among the solid-state imaging devices, some solid-state imaging device is configured by covering the surface of a silicon substrate, on which pixels that perform photoelectric conversion are formed, with an interlayer insulating film (a protective layer) of SiO2 or the like.
As one kind of performance of the solid-state imaging devices, in some case, a spectral characteristic as a sensitivity characteristic of each of wavelengths of incident light poses a problem. When a relation between the wavelength of the incident light and a light response output is represented, it is ideal that fluctuation in the light output response is gentle with respect to a change in the wavelength. On the other hand, in some case, the relation indicates a spectral characteristic in which the light response output fluctuates in a wavy manner with respect to a change in the wavelength. As a cause of the spectral characteristic, there is interference between light directly made incident on a photoelectric conversion element and light reflected on an interface of a protective layer provided on a semiconductor substrate. It is considered effective to suppress the interference of light to reduce such fluctuation in the spectral characteristic.
In general, in a solid-state imaging device, a pattern made of aluminum (hereinafter referred to as “aluminum wire” as appropriate) is provided as a light blocking section for reducing leakage of light to pixels adjacent to one another. Depending on a mode of forming an uneven shape on the surface of a protective layer, a satisfactory spectral characteristic is obtained. On the other hand, in some case, the aluminum wire formed in the inside of the protective layer tends to be exposed to the outside. The exposure of the aluminum wire to the outside leads to a fall in reliability of the solid-state imaging device because of corrosion or the like of the aluminum wire.
In the related art, a base layer pattern is formed on the interlayer insulating film, the base layer pattern is etched, and the base layer pattern is covered with an upper layer film by the CVD method to form a difference in height on a light incident surface of the solid-state imaging device. A pad electrode disposed on the interlayer insulating film is also covered with the base layer pattern and the upper layer film. Therefore, in addition to the steps, a step of etching the base layer pattern and the upper layer film is separately necessary to expose the pad electrode. Therefore, in the related art, in a manufacturing process for the solid-state imaging device, the number of steps increases to suppress the interference of light and it is difficult to hold down manufacturing cost.